1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * kernel/stacktrace.c
4 *
5 * Stack trace management functions
6 *
7 * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
8 */
9 #include <linux/sched/task_stack.h>
10 #include <linux/sched/debug.h>
11 #include <linux/sched.h>
12 #include <linux/kernel.h>
13 #include <linux/export.h>
14 #include <linux/kallsyms.h>
15 #include <linux/stacktrace.h>
16
17 /**
18 * stack_trace_print - Print the entries in the stack trace
19 * @entries: Pointer to storage array
20 * @nr_entries: Number of entries in the storage array
21 * @spaces: Number of leading spaces to print
22 */
stack_trace_print(const unsigned long * entries,unsigned int nr_entries,int spaces)23 void stack_trace_print(const unsigned long *entries, unsigned int nr_entries,
24 int spaces)
25 {
26 unsigned int i;
27
28 if (WARN_ON(!entries))
29 return;
30
31 for (i = 0; i < nr_entries; i++)
32 printk("%*c%pS\n", 1 + spaces, ' ', (void *)entries[i]);
33 }
34 EXPORT_SYMBOL_GPL(stack_trace_print);
35
36 /**
37 * stack_trace_snprint - Print the entries in the stack trace into a buffer
38 * @buf: Pointer to the print buffer
39 * @size: Size of the print buffer
40 * @entries: Pointer to storage array
41 * @nr_entries: Number of entries in the storage array
42 * @spaces: Number of leading spaces to print
43 *
44 * Return: Number of bytes printed.
45 */
stack_trace_snprint(char * buf,size_t size,const unsigned long * entries,unsigned int nr_entries,int spaces)46 int stack_trace_snprint(char *buf, size_t size, const unsigned long *entries,
47 unsigned int nr_entries, int spaces)
48 {
49 unsigned int generated, i, total = 0;
50
51 if (WARN_ON(!entries))
52 return 0;
53
54 for (i = 0; i < nr_entries && size; i++) {
55 generated = snprintf(buf, size, "%*c%pS\n", 1 + spaces, ' ',
56 (void *)entries[i]);
57
58 total += generated;
59 if (generated >= size) {
60 buf += size;
61 size = 0;
62 } else {
63 buf += generated;
64 size -= generated;
65 }
66 }
67
68 return total;
69 }
70 EXPORT_SYMBOL_GPL(stack_trace_snprint);
71
72 #ifdef CONFIG_ARCH_STACKWALK
73
74 struct stacktrace_cookie {
75 unsigned long *store;
76 unsigned int size;
77 unsigned int skip;
78 unsigned int len;
79 };
80
stack_trace_consume_entry(void * cookie,unsigned long addr)81 static bool stack_trace_consume_entry(void *cookie, unsigned long addr)
82 {
83 struct stacktrace_cookie *c = cookie;
84
85 if (c->len >= c->size)
86 return false;
87
88 if (c->skip > 0) {
89 c->skip--;
90 return true;
91 }
92 c->store[c->len++] = addr;
93 return c->len < c->size;
94 }
95
stack_trace_consume_entry_nosched(void * cookie,unsigned long addr)96 static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long addr)
97 {
98 if (in_sched_functions(addr))
99 return true;
100 return stack_trace_consume_entry(cookie, addr);
101 }
102
103 /**
104 * stack_trace_save - Save a stack trace into a storage array
105 * @store: Pointer to storage array
106 * @size: Size of the storage array
107 * @skipnr: Number of entries to skip at the start of the stack trace
108 *
109 * Return: Number of trace entries stored.
110 */
stack_trace_save(unsigned long * store,unsigned int size,unsigned int skipnr)111 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
112 unsigned int skipnr)
113 {
114 stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
115 struct stacktrace_cookie c = {
116 .store = store,
117 .size = size,
118 .skip = skipnr + 1,
119 };
120
121 arch_stack_walk(consume_entry, &c, current, NULL);
122 return c.len;
123 }
124 EXPORT_SYMBOL_GPL(stack_trace_save);
125
126 /**
127 * stack_trace_save_tsk - Save a task stack trace into a storage array
128 * @task: The task to examine
129 * @store: Pointer to storage array
130 * @size: Size of the storage array
131 * @skipnr: Number of entries to skip at the start of the stack trace
132 *
133 * Return: Number of trace entries stored.
134 */
stack_trace_save_tsk(struct task_struct * tsk,unsigned long * store,unsigned int size,unsigned int skipnr)135 unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
136 unsigned int size, unsigned int skipnr)
137 {
138 stack_trace_consume_fn consume_entry = stack_trace_consume_entry_nosched;
139 struct stacktrace_cookie c = {
140 .store = store,
141 .size = size,
142 /* skip this function if they are tracing us */
143 .skip = skipnr + (current == tsk),
144 };
145
146 if (!try_get_task_stack(tsk))
147 return 0;
148
149 arch_stack_walk(consume_entry, &c, tsk, NULL);
150 put_task_stack(tsk);
151 return c.len;
152 }
153 EXPORT_SYMBOL_GPL(stack_trace_save_tsk);
154
155 /**
156 * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
157 * @regs: Pointer to pt_regs to examine
158 * @store: Pointer to storage array
159 * @size: Size of the storage array
160 * @skipnr: Number of entries to skip at the start of the stack trace
161 *
162 * Return: Number of trace entries stored.
163 */
stack_trace_save_regs(struct pt_regs * regs,unsigned long * store,unsigned int size,unsigned int skipnr)164 unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
165 unsigned int size, unsigned int skipnr)
166 {
167 stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
168 struct stacktrace_cookie c = {
169 .store = store,
170 .size = size,
171 .skip = skipnr,
172 };
173
174 arch_stack_walk(consume_entry, &c, current, regs);
175 return c.len;
176 }
177 EXPORT_SYMBOL_GPL(stack_trace_save_regs);
178
179 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
180 /**
181 * stack_trace_save_tsk_reliable - Save task stack with verification
182 * @tsk: Pointer to the task to examine
183 * @store: Pointer to storage array
184 * @size: Size of the storage array
185 *
186 * Return: An error if it detects any unreliable features of the
187 * stack. Otherwise it guarantees that the stack trace is
188 * reliable and returns the number of entries stored.
189 *
190 * If the task is not 'current', the caller *must* ensure the task is inactive.
191 */
stack_trace_save_tsk_reliable(struct task_struct * tsk,unsigned long * store,unsigned int size)192 int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
193 unsigned int size)
194 {
195 stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
196 struct stacktrace_cookie c = {
197 .store = store,
198 .size = size,
199 };
200 int ret;
201
202 /*
203 * If the task doesn't have a stack (e.g., a zombie), the stack is
204 * "reliably" empty.
205 */
206 if (!try_get_task_stack(tsk))
207 return 0;
208
209 ret = arch_stack_walk_reliable(consume_entry, &c, tsk);
210 put_task_stack(tsk);
211 return ret ? ret : c.len;
212 }
213 #endif
214
215 #ifdef CONFIG_USER_STACKTRACE_SUPPORT
216 /**
217 * stack_trace_save_user - Save a user space stack trace into a storage array
218 * @store: Pointer to storage array
219 * @size: Size of the storage array
220 *
221 * Return: Number of trace entries stored.
222 */
stack_trace_save_user(unsigned long * store,unsigned int size)223 unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
224 {
225 stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
226 struct stacktrace_cookie c = {
227 .store = store,
228 .size = size,
229 };
230 mm_segment_t fs;
231
232 /* Trace user stack if not a kernel thread */
233 if (current->flags & PF_KTHREAD)
234 return 0;
235
236 fs = force_uaccess_begin();
237 arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
238 force_uaccess_end(fs);
239
240 return c.len;
241 }
242 #endif
243
244 #else /* CONFIG_ARCH_STACKWALK */
245
246 /*
247 * Architectures that do not implement save_stack_trace_*()
248 * get these weak aliases and once-per-bootup warnings
249 * (whenever this facility is utilized - for example by procfs):
250 */
251 __weak void
save_stack_trace_tsk(struct task_struct * tsk,struct stack_trace * trace)252 save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
253 {
254 WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
255 }
256
257 __weak void
save_stack_trace_regs(struct pt_regs * regs,struct stack_trace * trace)258 save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
259 {
260 WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
261 }
262
263 /**
264 * stack_trace_save - Save a stack trace into a storage array
265 * @store: Pointer to storage array
266 * @size: Size of the storage array
267 * @skipnr: Number of entries to skip at the start of the stack trace
268 *
269 * Return: Number of trace entries stored
270 */
stack_trace_save(unsigned long * store,unsigned int size,unsigned int skipnr)271 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
272 unsigned int skipnr)
273 {
274 struct stack_trace trace = {
275 .entries = store,
276 .max_entries = size,
277 .skip = skipnr + 1,
278 };
279
280 save_stack_trace(&trace);
281 return trace.nr_entries;
282 }
283 EXPORT_SYMBOL_GPL(stack_trace_save);
284
285 /**
286 * stack_trace_save_tsk - Save a task stack trace into a storage array
287 * @task: The task to examine
288 * @store: Pointer to storage array
289 * @size: Size of the storage array
290 * @skipnr: Number of entries to skip at the start of the stack trace
291 *
292 * Return: Number of trace entries stored
293 */
stack_trace_save_tsk(struct task_struct * task,unsigned long * store,unsigned int size,unsigned int skipnr)294 unsigned int stack_trace_save_tsk(struct task_struct *task,
295 unsigned long *store, unsigned int size,
296 unsigned int skipnr)
297 {
298 struct stack_trace trace = {
299 .entries = store,
300 .max_entries = size,
301 /* skip this function if they are tracing us */
302 .skip = skipnr + (current == task),
303 };
304
305 save_stack_trace_tsk(task, &trace);
306 return trace.nr_entries;
307 }
308
309 /**
310 * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
311 * @regs: Pointer to pt_regs to examine
312 * @store: Pointer to storage array
313 * @size: Size of the storage array
314 * @skipnr: Number of entries to skip at the start of the stack trace
315 *
316 * Return: Number of trace entries stored
317 */
stack_trace_save_regs(struct pt_regs * regs,unsigned long * store,unsigned int size,unsigned int skipnr)318 unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
319 unsigned int size, unsigned int skipnr)
320 {
321 struct stack_trace trace = {
322 .entries = store,
323 .max_entries = size,
324 .skip = skipnr,
325 };
326
327 save_stack_trace_regs(regs, &trace);
328 return trace.nr_entries;
329 }
330
331 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
332 /**
333 * stack_trace_save_tsk_reliable - Save task stack with verification
334 * @tsk: Pointer to the task to examine
335 * @store: Pointer to storage array
336 * @size: Size of the storage array
337 *
338 * Return: An error if it detects any unreliable features of the
339 * stack. Otherwise it guarantees that the stack trace is
340 * reliable and returns the number of entries stored.
341 *
342 * If the task is not 'current', the caller *must* ensure the task is inactive.
343 */
stack_trace_save_tsk_reliable(struct task_struct * tsk,unsigned long * store,unsigned int size)344 int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
345 unsigned int size)
346 {
347 struct stack_trace trace = {
348 .entries = store,
349 .max_entries = size,
350 };
351 int ret = save_stack_trace_tsk_reliable(tsk, &trace);
352
353 return ret ? ret : trace.nr_entries;
354 }
355 #endif
356
357 #ifdef CONFIG_USER_STACKTRACE_SUPPORT
358 /**
359 * stack_trace_save_user - Save a user space stack trace into a storage array
360 * @store: Pointer to storage array
361 * @size: Size of the storage array
362 *
363 * Return: Number of trace entries stored
364 */
stack_trace_save_user(unsigned long * store,unsigned int size)365 unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
366 {
367 struct stack_trace trace = {
368 .entries = store,
369 .max_entries = size,
370 };
371
372 save_stack_trace_user(&trace);
373 return trace.nr_entries;
374 }
375 #endif /* CONFIG_USER_STACKTRACE_SUPPORT */
376
377 #endif /* !CONFIG_ARCH_STACKWALK */
378